This invention relates generally to a surveying instrument, or apparatus, and more particularly to a surveying instrument providing both an optical sighting scope and planar referencing device that generates a datum plane of light for surveying tasks.
In order to perform a surveying task, such as locating footer forms 10a, 10b using a conventional transit 12, a first operator 11 must observe the image of stakes 14, or the like, being moved about by a remote worker 13a, while the first operator uses arm and hand or voice signals to communicate movement to the remote worker (FIG. 1). Once the line is established in this manner, height or elevation may be established by using a measuring stick 16, which is raised or lowered by the remote worker 13b in response to communications from the first operator, until the desired elevation is reached.
While such conventional technique is suitable when two or more workers are available and under fairly controlled site conditions, the effort required increases enormously if the same individual must make the observation and adjust the implement observed, especially when the site is overgrown or otherwise presents difficult terrain. In order to allow an individual operator to perform a surveying task, devices have been developed that generate a datum plane of light, which may be set up at a particular vertical or horizontal plane and used by the same operator, holding a remote light sensor, to establish required headings and elevations.
Prior art datum plane light generators have not met their full potential because they have been too expensive and require bulky power supplies in order to power the gas laser and rotating motor typically used in such devices to generate a light plane. Accordingly, such devices have been relegated to fairly specialized applications and have not found general use.